A moment on special teams in which the defense manages to deflect a field goal attempt by the opposing kicker, recover the ball the block, and return it to their end zone without being stopped by the other team. A blocked field goal touchdown is treated like any other touchdown. Blocked field goal touchdowns are rare, since the block has to be at a correct angle to be collected by an unimpeded defensive player in a manner in which he can return the ball for a score.
Blocked field goal touchdowns are extremely rare due to the large number of factors that need to go right in order to return the block. NFL kickers are extremely effective, and do not give the defense many kicks that can be blocked. The defense has to call the right play and execute it perfectly to get a hand on a kick, and the ball has to bounce just right to be recovered by the defense at all. The defense also has to be able to collect the ball with an open avenue to the end zone. A blocked field goal touchdown can be an enormous momentum swing, because it changes the play from a potential three points for the offense and turns it into six for the defense.